Question: Why is a collective reading of The Book of Zohar preferable? Is this related to the laws of psychology?
Answer: No. The upper world is built upon bestowal and love, upon the connection and integration of characteristics.
Kabbalists wrote extensively about these conditions. If relationships exist between friends in which they complement each other, connect, and so forth, then The Book of Zohar begins to illuminate them and fill them. Otherwise, it has no influence on the person.
From the Kabbalah Lesson in Russian 2/12/17
To Open The Book Of Zohar
The Zohar—A Tool For Working On Yourself
The Book Of Zohar—The Most Important Condition